1. Field
The present invention relates to rare gas-halogen excimer lasers and, in particular, to increasing the operational lifetime, reliability, efficiency, and/or performance of such lasers.
2. Description of the Related Art
An excimer laser uses a rare gas such as krypton (Kr), xenon (Xe), argon (Ar), or neon (Ne), and a halide gas or a gas containing a halide, for example fluorine (F2) or hydrogen chloride (HCl), as the active components. The active components, and possibly other gases, are contained in a pressure vessel provided with longitudinally extending lasing electrodes for inducing a transverse electrical discharge in the gases. The discharge causes the formation of excited rare gas-halide molecules whose disassociation results in the emission of ultraviolet photons constituting the laser light. Many excimer lasers use xenon chloride (XeCl) as the medium for generating light at a specific wavelength (e.g., at about 308 nanometers (nm)). The laser further comprises mirrors or reflective surfaces that form an optical cavity to establish an optical resonance condition. Such a system is also described in U.S. patent application Ser. No. 10/776,463, filed Feb. 11, 2004, entitled “Rare Gas-Halogen Excimer Laser with Baffles,” which is incorporated herein by reference in its entirety. The chamber may include inlet and outlet ports for flow of gases into and out of the chamber.
Such lasers may optionally include a feedback system wherein a fraction of the light in the output laser beam is extracted to monitor the performance of the laser. What is needed are efficient and effective feedback systems for excimer lasers.